Cellular Respiration

1
Cellular Respiration

• Unit III
• Chapter 9

2
Chemical Energy Food

• How much energy is in food?
• A lot 1 gram of sugar glucose, when burned in
  the presence of oxygen, releases 3811 calories of
  heat energy
• A calorie is the amount of energy required to
  raise the temperature of 1 gram of water 1 degree
  Celcius

3
Overview of Cellular Respiration

• Cellular respiration is the process that releases
  energy by breaking down food molecules in the
  presence of oxygen
• Organisms that respire animals, fungi, plants
  (during night hours)
• Cellular respiration requires a food molecule
  (such as glucose), oxygen, and it gives off
  carbon dioxide
• Because is occurs in the PRESENCE of OXYGEN,
  cellular respiration is known as AEROBIC
  respiration

4
Chemical Formula for Cellular Respiration

• The chemical formula for cellular respiration is
• 6O2 C6H12O6 ? 6 CO2 6 H2O Energy
• oxygen glucose ? carbon dioxide water
  energy
• The reactants of cellular respiration are
• oxygen (O2) glucose (C6H12O6)
• The products of cellular respiration are
• carbon dioxide (CO2) and water (H2O)
• The 3 main stages of cellular respiration are
• Glycolysis
• Krebs Cycle (Citric Acid Cycle)
• Electron Transport

5
Visual Overview of Cellular Respiration
Krebs Cycle
6
Glycolysis

• The first set of reactions in cellular
  respiration is glycolysis
• Glycolysis is the process in which 1 molecule of
  glucose is broken in half, producing 2 molecules
  of pyruvic acid
• Glycolysis occurs in the cytoplasm of the cell
• Glycolysis produces a total of 4 ATP, but
  requires 2 ATP in the beginning to get through
  the membrane of the mitochondria
• Therefore, the NET ATP YIELD of glycolysis is 2
  ATP

7
The Krebs Cycle

• In the presence of oxygen, the pyruvic acid
  produced during glycolysis passes to the second
  stage of cellular respiration the Krebs cycle
• During the Krebs cycle, pyruvic acid is broken
  down into carbon dioxide in a series of
  energy-extracting reactions
• Every time you exhale, you expel the CO2 produced
  by the Krebs cycle
• For each turn of the cycle, 5 pairs of high
  energy electrons are captured by the carrier
  molecules NADH and FADH2

8
Electron Transport

• Following the Krebs cycle, the electrons captured
  by NADH and FADH2 are passed to the electron
  transport chain
• The electron transport chain uses the high-energy
  electrons from the Krebs cycle to convert ADP to
  ATP
• Every time 2 high energy electrons transport down
  the ETC, their energy is used to transport H
  across the inner membrane of the
  mitochondriathis creates a charge on the
  inside of the membrane and a charge in the
  matrix of the mitochondria
• As a result of this charge difference, H ions
  escape through channel proteins called ATP
  synthase causing it to rotate
• Each time it rotates, the enzyme ATP synthase
  grabs a low energy ADP and attaches a phosphate,
  forming high-energy ATP

9
Electron Transport Chain
inner membrane space
inner membrane
Matrix of mitochondria
10
The Energy Totals

• The complete breakdown of 1 glucose molecule
  through cellular respiration results in the
  production of 36 molecules of ATP

11
Respiration in the Absence of Oxygen

• When oxygen is NOT present, glycolysis is
  followed by a different pathway called
  fermentation
• Fermentation releases energy from food molecules
  in the absence of oxygen
• Because fermentation does not require oxygen, it
  is said to be anaerobic
• The 2 main types of fermentation are alcoholic
  fermentation and lactic acid fermentation